Commonly it is essential that, for proper operation of optical apparatus of which the assembly will form a part, the elements of the assembly be precisely positioned with respect to one another; in the example mentioned the position of the lens in the plane of the flat surface of the mounting plate may be critical. A method in accordance with the present invention permits adjustment of the optical elements while the adhesive is still liquid until the correct relative positioning is achieved, this being ascertainable by an appropriate optical technique, and the subsequent rapid curing of the adhesive by flooding the elements with the electromagnetic radiation to fix these elements in the desired position.
This possibility is of significance in the field of photocomposition, and more particularly in the photocomposing technique employing a fixed character font carrying an array of characters, and an assembly of small lenses, one for each character, herein referred to as lenslets, the lenslets being arranged in an array corresponding to the array of characters in the font, such that when the assembly is correctly located in the photocomposing machine, the array of lenslets is disposed in a plane forward of the character font, which may comprise an opaque plate carrying an array of transparent characters, each lenslet being displaced from its respective character by a distance corresponding to its focal length. When the character font is suitably illuminated from behind, light carrying character information is collimated when passing through the individual lenslets and thereafter passes to a suitable optical system which focusses the characters onto a photosensitive recording element such as a photographic plate or film. This optical system is such that the images of each of the characters can be focussed at a single common image position and accordingly, by appropriate sequential selection of the characters projected from the lenslet assembly and intermittent displacement of the photosensitive recording element relative to this common image position, the exposed characters can be arranged side by side to produce successive lines of text composition on the recording element, while the character font remains stationary.
To obtain high quality composition with accurate alignment and justification of the characters, it is necessary to ensure that images of all of the characters are precisely located at the common image position. This requires a high degree of accuracy in the positioning of the characters in the font and of the lenslets in the lenslet assembly, to ensure that each lenslet aligns accurately with its respective character in the font plate in the assembled apparatus. The process by which the font is produced, usually a photographic process, readily permits such accuracy in character positioning to be obtained. The required accuracy in lenslets positioning is, however, not so readily achieved and heretofore the techniques employed have involved complicated and costly mechanical arrangements for the individual adjustment of the positions of the lenslets, or alternatively individual optical assemblies of lenses and adjustable prisms to alter laterally the positions of the light beams leaving the lenslets, after incorporating the assembly in the machine.
A method according to the present invention may be employed to advantage in this field of photocomposition, to make an assembly with the lenslets adjusted and fixed prior to the mounting of the assembly in the machine.